[Leetcode] Subsets II

Given a collection of integers that might contain duplicates, S, return all possible subsets.

Note:

Elements in a subset must be in non-descending order.
The solution set must not contain duplicate subsets.

For example,
If S = [1, 2], a solution is:

[
[2],
[1],
[1, 2],
[2, 2],
[1, 2],
[]
]
This once made me catch chicken very much... Why is a bad dfs used this time? It is a one-time pass, and it is a large set of 80 ms .... Too Ironic...

class Solution {    set<vector<int>> result;public:    void dfs(vector<int>&S, int i, vector<int> tmp){        if(i == S.size()){            sort(tmp.begin(), tmp.end());            result.insert(tmp);            return;        }        dfs(S, i+1, tmp);                tmp.push_back(S[i]);        dfs(S, i+1, tmp);                    }        vector<vector<int> > subsetsWithDup(vector<int> &S) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        result.clear();        vector<int> tmp;        dfs(S, 0, tmp);        set<vector<int>>::iterator it;                vector<vector<int>> ret;        for(it = result.begin(); it!=result.end(); it++){            ret.push_back(*it);        }                return ret;           }};